
the electrons spend more time in vicinity of one atom. In this case, electrons will
spend more time in the region of fluorine.
The type of bond formed in this way is called polar covalent bond or simply
polar bond.
The compounds with polar bonds their molecules have one end positively
partially charged and the other end negatively slightly charged. Thus, the bond in
polar compounds has some partial ionic characters.
In the periodic table, the electro negativity decreases as one goes down a group
but it increases across the period from left to right.
The opposite of the electro negativity is electro positivity which is the ability of
an atom to lose its outer most electrons in order to achieve stability. Electro
positivity increases down a group. Potassium is the most electro positive
element.
Properties of covalent compounds:
Are usually gases, liquids or solids of low melting points and boiling points.
The melting points are low because of the weak Van der Waals forces of attraction.
Giant molecular substances have higher meting points because the whole structure is
held together by strong covalent bonds with the molecules.
Generally they do not conduct electricity since when molten or dissolved in water they
do not ionize save for HCl and some few acids. The HCl, when dissolved in water, it
ionizes to produce H
+
and Cl
-
.
In general, they do not dissolve in water unless they react with it to form ion s.
However, water is an excellent solvent and can interact with and dissolve some covalent
molecules e.g. Sugars.
They dissolve in organic solvent such as petrol, carbon tetra chloride. etc.
Examples of covalent compounds include sugar, ammonia, carbon dioxide, water etc
DIFFERENCES BETWEEN IONIC AND COVALENT BONDS:
When salt (ionic) e.g. sodium chloride and sugar (covalent) are heated equally, sugar takes little
time to melt than the salt.
I. This indicates that ionic bonds are stronger than the covalent bonds.
II. Ionic bonds are formed by loosing or gaining valence electrons while the covalent bonds
are formed by sharing of electrons.
III. Ionic bonds are because of electrostatic forces while covalent bonds are due to
intermolecular forces.
IV. Ionic bonds occur between a metal and a non-metal while covalent bond involves non-
metals.
DIFFERENCES BETWEEN IONIC COMPOUNDS AND COVALENT COMPOUNDS: